Aikataajuusanalyysiä

Aikataajuusanalyysiä, often translated as time-frequency analysis, is a technique used to simultaneously analyze the frequency content of a signal as it changes over time. Unlike traditional Fourier analysis, which provides a global frequency spectrum of an entire signal, time-frequency analysis offers a more detailed view of how frequencies evolve within the signal. This is particularly useful for non-stationary signals, where the frequency components are not constant.

Various methods exist for time-frequency analysis, each with its own strengths and weaknesses. Common techniques include the Short-Time Fourier Transform (STFT), wavelets, and the Wigner-Ville distribution. The STFT involves breaking the signal into short segments and performing a Fourier transform on each segment, providing a time-localized frequency spectrum. Wavelet analysis uses scaled and translated versions of a "mother wavelet" to decompose the signal, offering good time and frequency resolution depending on the chosen wavelet. The Wigner-Ville distribution, while offering high resolution, can suffer from cross-term interference for multi-component signals.

The applications of time-frequency analysis are widespread across many scientific and engineering disciplines. It is extensively used in speech and audio processing for tasks like voice recognition and music analysis, in biomedical engineering for analyzing physiological signals such as EEG and ECG, and in mechanical engineering for vibration analysis and fault detection in machinery. Other fields include radar signal processing, image analysis, and geophysics. The ability to understand how frequency content changes over time allows for a deeper understanding and more effective processing of complex signals.